The present invention relates to a color sorting apparatus for granular objects such as agricultural granular material such as cereals, beans or the like and industrial granular material such as pellets, ores or the like.
A Color sorting apparatus of the kind referred to above is disclosed in Japanese patent application 225065/85 which was filed on Oct. 9, 1985 and laid open to the public on Apr. 16, 1987 as the Japanese patent application Laid-Open No. 83078/87 (62-83078A), and comprises a plurality of sorting units arranged in parallel relation to each other. Detecting positions of the respective sorting units are spaced from each other along a horizontal straight line. In each of the sorting units, the granular objects fed by a feeder are guided by a chute so as to be transported along a predetermined path passing through the detecting position of the sorting unit. A light source illuminates the granular objects passing through the detecting position. Three detectors are disposed at the detecting position in angularly spaced relation to each other around the predetermined path.
Each of the three detectors comprises a background-forming means and photodetector elements located on the opposite side of the detecting position from the background-forming means. The photodetector elements receive light reflected from and/or transmitted through the granular objects passing through the detecting position to deliver signals. A control circuit device is responsive to the signals from the photodetector elements representing undesirable granular objects to deliver an actuating signal.
A deflector located below the detecting position is operative in response to the actuating signal from the control circuit device to deflect the undesirable granular objects out of the predetermined path. Thus, desirable granular objects are separated from the undesirable granular objects.
In the color sorting apparatus as described above, the granular objects are directed along the chute by the action of gravity while being in sliding contact with the bottom surface of the chute.
Because the resistances against the motion of the granular objects due to the sliding contact thereof with the bottom surface of the chute change depending on the contact states of the granular particles with the chute, loci of the respective granular objects are changed or disturbed, so that there is fear that the granular objects may not fall along the predetermined path passing through the detecting position. For this reason, it would be difficult for the detectors to accurately detect the undesirable granular objects in some kinds of granular objects.
Further, in the above-described color sorting apparatus, the arrangement of the three detectors in one of a pair of adjacent sorting units is the same as that of the three detectors in the other sorting unit. For this reason, considerable installation area and space are required for the color sorting apparatus, and this results in an increase in total investment in the facilities concerned.
Japanese patent application Laid-Open No. 61-269030 by T. Satake, inventor of the present invention, discloses a color sorting apparatus in which various kinds of granular objects are sorted without changing background means.
U.S. Pat. No. 4,235,342 issued to Braham on Nov. 25, 1980 also discloses a color sorting apparatus in which various kinds of granular objects are sorted without changing background means.
U.S. Pat. No. 3,283,896 issued to Jirik et al on Nov. 8, 1966 discloses a tubular guide member mounted vertically. U.S. Pat. No. 3,482,686 issued to Wood on Dec. 9, 1969 discloses a generally funnel-shaped chute, i.e., tubular guide member.